Autobiography of Sir John Rennie, F.R.S. 2
My father at that period had one department of his business exclusively
devoted to practical mechanics, that is, to the making of machinery of
all kinds; this department, although it formed by no means the principal
part of his profession, nevertheless enabled him to make experiments
which were of great value in the other departments of his business,
and was by no means unprofitable, as the importance of machinery and
mechanical contrivances was then to a certain extent appreciated, and
was daily becoming more so. My father always said that theoretical and
practical mechanics were the true foundations of all civil engineering;
and he therefore insisted that as I had to a certain extent learned the
theoretical, so I must now learn the practical part. I was therefore sent
into the mechanical department, and commenced work planing and sawing
boards, making patterns, and other similar works. After this I was put
to turning both wood and metal; and although I did not attain complete
practical efficiency in these departments, which would have required
several years, nevertheless I learned sufficient to enable me to become a
tolerable judge of workmanship.
I was then put into the drawing office, where I learned to copy
geometrical plans, by which, in a short time, in combination with what I
had acquired in the workshop, I gained a general knowledge of design and
construction.
My time was employed in this manner about eight hours daily, but my
evenings were devoted to the acquisition of geometry, algebra, and
trigonometry, plane and spherical; also astronomy under the late
Astronomer Royal, Mr. Pond, and his father-in-law, Dr. Bradley, and
in learning French, Italian, and German. Having acquired to a certain
extent a proficiency in the mathematical sciences, I was placed under the
direction of the late Mr. Francis Giles, a land surveyor of considerable
experience and ability, who was generally employed by my father to make
his various hydraulic surveys for canals and harbours under his immediate
direction, which Mr. Giles executed with his usual fidelity and ability.
Under Mr. Giles I learned the use of the chain, level, and theodolite,
and was enabled to apply my theoretical knowledge in trigonometry, plane
and spherical, to practice. About this period, viz. the year 1813,
having obtained a tolerable knowledge of the rudiments of my profession,
both theoretical and practical, my father determined to place upon my
shoulders a certain degree of responsibility, and put me under the
direction of that late worthy and excellent man, Mr. James Hollingsworth,
whom my father had appointed to be resident engineer of the Waterloo
Bridge, which was then building. I felt the responsibility of this office
a good deal, and entered upon it with every determination and desire
to meet my father’s approbation; and during the inclement winter of
1813-14, when the frost lasted about two months, and the Thames above
London Bridge was frozen over for several weeks, I was obliged to attend
the piling of the foundations of the first and second piers on the Surrey
side of the river night and day for three days each week, which severely
tried my constitution.
At this period Vauxhall Bridge was also in course of construction, and I
was directed by my father to attend to this also, under Mr. Jones, the
resident engineer; but they had scarcely finished the Middlesex abutment
up to the springing of the first arch, and were preparing the caisson
for founding the first pier, when the Company found that they had not
sufficient funds to carry into effect Mr. Rennie’s design, which was very
beautiful. The bridge was to be made entirely of the fine blue sandstone
from Dundee, and was to consist of seven arches, segments of circles,
the centre arch being 110 feet span, with a rise or versed sine of 19
feet, and depth of keystone 4 feet 6 inches; piers 18 feet 6 inches thick
at the springing of the arch, the two arches next the centre being 105
feet span each, with a rise or versed sine of 17 feet, keystone 4 feet
5 inches, and springing stones 9 feet long, and the two piers 17 feet 6
inches thick each. The two next arches were 100 feet span, with a rise
or versed sine of 15 feet, keystones 4 feet 4 inches, and springers
9 feet, and piers 17 feet thick each; the two sub or shore arches 90
feet span each, with a rise or versed sine of 13 feet, keystones 4
feet, and springers 8 feet, abutments 21 feet thick at the springing,
having a total width of waterway of 700 feet. The arches were surmounted
by a Roman Doric cornice and plain block and plinth parapet, and the
projecting points of the piers were surmounted by solid square pilasters,
with a niche in the centre. The roadway was 34 feet wide between the
parapets, and was formed by a very flat segment of a circle rising 1 in
53. The piers were intended to be founded by caissons resting upon a
platform supported by bearing and surrounded by sheeting piles. This was
upon the whole a very elegant, light, and chaste design. Finding that the
Company had not sufficient funds to carry into effect the stone design,
Mr. Rennie proposed another wholly of iron, consisting of eleven arches,
with a total waterway of 732 feet, supported upon cast-iron columns
filled with masonry and resting upon a platform supported upon piles and
surrounded by sheeting piles. The centre arch was to be 86 feet span and
8 feet rise, and the others diminishing regularly to each end so as to
enable the roadway to be formed into a graceful curve rising 1 foot in
60. This also was an extremely light, elegant, and economical design.
The total cost of this elegant design was estimated at 100,000_l._, and
would have been executed first, but at that time even this amount was not
forthcoming. The works then stopped, and some time elapsed before the
Company was resumed, and ultimately constructed the present bridge.
In the year 1814-15 my father was appointed engineer-in-chief of the
Southwark Bridge Company, and as this was proposed to be constructed in
the narrowest part of the river between Blackfriars and the Old London
Bridge, considerable opposition was made to the Act of Parliament for its
construction by the Corporation of London and the Conservators of the
river, on account of the obstruction which they said the bridge would
offer to the navigation; this however was finally overcome, but it was
decided by Parliament that the bridge should be constructed with as large
arches as possible. Accordingly Mr. Rennie submitted a design consisting
of three cast-iron arches, the centre being 240 feet span, with a versed
sine of 24 feet, and two side arches of 210 feet each, with a versed sine
or rise of 18 feet 10 inches each, with piers of 24 feet wide each at the
springing, thus giving a clear lineal waterway of 660 feet, which was a
great deal more than that of the Old London Bridge at that time existing.
This design was approved of and ordered to be carried into effect. By
this time, with the experience of the Waterloo and Vauxhall bridges and
my other studies, I had gained considerable knowledge in bridge building,
and my father was anxious to give me as much encouragement as possible;
although, therefore, he appointed a worthy and practical man, Mr. Meston,
as nominally the resident engineer, yet he confided to me the arduous
task of making out the working drawings under his own direction, and
of carrying them into effect. I therefore felt highly gratified with
this great mark of confidence, and devoted my whole energies to the
work night and day. The ironwork was carried into effect by Messrs.
Walker, of Rotherham, under the able management of their experienced and
able superintendent, Mr. Yeats, and the masonry and piling under the
well-known contractors, Messrs. Jolliffe and Banks; and Mr. Meston, the
resident engineer, faithfully discharged his duties.
As these arches were the largest of the kind ever constructed,
considerable doubts as to their stability occurred to many, and the
subject was discussed amongst scientific men with considerable energy;
and amongst others, the celebrated Dr. Young undertook to investigate
Mr. Rennie’s calculations, and came to the conclusion that the bridge
was well designed, and would be a perfectly safe and stable structure,
and equal to the support of any weight or amount of traffic which could
be brought over it. But in order to fulfil these conditions, it was
absolutely necessary that every detail of materials and workmanship
should be worked out with the greatest skill and accuracy.
As the arches were of such great span with so small rise, the pressure
upon the piers and abutments was chiefly lateral; it therefore became
necessary to construct them in such a manner that they should offer
the most effectual resistance to this pressure. In consequence, the
foundations of the abutments were made on an incline, and the masonry
from thence upwards to the springing of the arches was made to consist
of a series of courses radiating upwards until they reached the angle
of the springing courses; so that, in point of fact, the abutments
formed, as it were, a continuation of the side arches to their base;
and in order to connect the courses of masonry more solidly together,
the courses were connected with each other from the top to the bottom
by several series of vertical bond stones, thus forming one solid
immovable mass. These abutments were supported on a platform composed
of piles, double sleepers, and planking, the piles being 20 feet long,
12 inches in diameter in the middle, and driven solidly into the ground
at right angles to the inclination of the foundation. As the pressure
upon the piers was nearly equal on both sides, it was necessary that the
foundations should be laid level. These also rest upon a wooden platform
of double sills and planking, lying upon piles of the same dimensions
as those of the abutments, driven vertically into the ground below, and
the courses of masonry, which were laid horizontally, were connected
together in the vertical direction by a series of bond stones in a
similar manner to those of the abutments. The abutments and piers were
founded many feet below low-water mark of spring tides, so as to be below
the reach of any possible scour of the river. Those parts of the piers
from immediately below the springing of the arches to a point above the
top of the main solid ribs of the arches were composed of large blocks
of stone set nearly vertically, breaking bond laterally and vertically
with each other, and in the centre of this part of the piers there was a
set of keystones 12 feet long and 2 feet thick, tapering on each side,
forming so many stone wedges. These were very finely worked on all sides.
These wedge stones broke bond laterally with the blocks in front of
them, and were firmly driven into their places for a depth of 2 feet by
means of heavy wooden rams. The masonry of the pilasters and salient
angles of the piers is of the same character as those of the interior
of the pier before described, and worked into them in the same manner,
so as to form one solid bond from one point of the pier to the other.
The whole of the exterior of this part of the piers, as well as of the
abutments, is cased with granite from Scotland or Cornwall; and it was
necessary that the blocks forming this casing should be of the largest
kind, which hitherto was quite unusual, particularly for the facing of
the abutments from whence the arches were to spring, which required
blocks from 15 to 20 tons. These were of such unusual magnitude, and
nothing of the kind had hitherto been used in London, or even elsewhere
in England, that the contractors made considerable objection to obtaining
them, and even went so far as to say that it could not be done. I was
perfectly convinced that it could be done, and that it was merely a
question of a little extra expense, and strongly recommended my father
to insist upon it, as it was absolutely necessary for the security of
the bridge; and he did so, and directed me to proceed to Aberdeen for
the purpose of obtaining them. I accordingly started for Aberdeen; and
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